| Summary: | 博士 === 長庚大學 === 生物醫學研究所 === 98 === Different models of neurogenic stress were used to explore the changes in levels of endogenous interleukin-1β (IL-1β), an essential chemical mediator, in the paraventricular nucleus (PVN) of the hypothalamus due to its currently unclear role. In the present study, adult male Sprague-Dawley rats were subjected to varied neurogenic stresses (acute footshock, chronic footshock, or conditioning fear) and then sacrificed at 2 hrs or 5 hrs. Results showed that levels of IL-1β mRNA expression and IL-1β-innunoreactivity (ir) were up-regulated in both PVN and hippocampus. Immunohistochemical studies also showed that FOS-ir and IL-1β-ir were co-localized in the PVN, indicates that IL-1β-ir cells were activated in response to stress. Double immunohistochemical stainings revealed that astrocytes were capable to synthesize IL-1β in both PVN and hippocampus. Via electromobility shift assay, we further demonstrated an activation of nuclear NF-κB signaling pathway in conditioning fear paradigm. In addition, immunohistochemical studies showed that phopho-ERK1/2-ir were elevated in response to neurogenic stress. From these in vivo studies, we conclude that neurogenic stressors would affect endogenous IL-1β expression in the PVN and hippocampus. These findings suggest IL-1β may play an essential role in the central regulation of stress response. Although noradrenergic inputs from the brainstem are known to be critical for the central stress response and it was suggested that endogenous IL-1β involves in NE-induced release of CRH from the PVN, no IL-1 receptor on PVN CRH neurons however, has been identified. Therefore, we hypothesized that the action of IL-1β in the PVN would be mediated by local circuits through other modulators within the PVN. Organotypic cultures of neonatal rat PVN were conducted to characterize the role of IL-1β in the regulation of NE-evoked CRH release. Pharmacological treatments of NE or IL-1β elicited NO release from the PVN in vitro, implying that local NO might be a potential candidate in modulating the action of IL-1β. Short-term (within 60 min) NE treatments significantly increased IL-1β and CRH release, detected by ELISA in the PVN culture. In addition, real-time PCR showed long-term (16 hrs) NE treatments also significantly up-regulated the expression of CRH mRNA. Further, the administration of IL-1β or NO donor, sodium nitroprusside, also induced CRH release. Consistent with this finding, we also demonstrated that IL-1 receptor antagonist or NOS inhibitor L-NNA attenuated the NE-induced CRH release. On the other hand, long-term application of sodium nitroprusside significantly elevated CRH mRNA. When NE was co-incubated with L-NNA, the treatment could attenuate the enhanced CRH mRNA level induced by NE. These results suggest that IL-1β and NO are participated in the NE-induced CRH release. Moreover, we found that application of L-NNA attenuated IL-1β-induced CRH release, indicating IL-1β-induced CRH release is likely to be mediated by NO. In summary, the current study demonstrates that IL-1β plays a significant role in NE-induced CRH release, in addition the cellular interactions in the neuroendocrine PVN could be networked by local NO actions.
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